The incident happened around 2.35pm near Causey Park.
North East Live Traffic, at 4.19pm, tweeted: ‘Northbound is closed for air ambulance, police & recovery.’
The road had been closed in both directions earlier.
Northumberland Fire and Rescue Service tweeted: ‘Crews from Pegswood are currently in attendance at an RTC on the A1 Causey Park.
‘Please avoid the area if possible.’